I personally HATE skipping first and second levels. To me, it is an important part of the character arc and I really enjoy low level play. In my current campaign our first session was a zero-level funnel.
Anyway, if you are going to skip levels 1 and 2, I'm not sure I see the point in making them earn the XP for those levels and 3rd before they can level up to 4th. I suppose it does have the advantage of extending tier one play while avoiding the the squishy levels. I wonder why you don't just go full milestone leveling? Decide how many sessions, about, you want to play at certain levels and level up when it feels right for the story.